Low-inductance busbar system for a matrix converter

ABSTRACT

A low-inductivity busbar system for a matrix converter which includes a plurality of switch elements, in particular semiconductor switches, disposed in a 3×3 matrix. The matrix converter is connected on the network side by the busbar system to a plurality of capacitor elements for supply of three input voltage potentials to the matrix converter. The busbar system includes of a plurality of busbar sections disposed in two levels and isolated from one another.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application is a continuation of prior filed copending PCTInternational application no. PCT/DE01/02793, filed Jul. 23, 2001, whichwas not published in English and which designated the United States andon which priority is claimed under 35 U.S.C. §120, the disclosure ofwhich is hereby incorporated by reference.

[0002] This application claims the priority of German PatentApplication, Serial No. 100 37 970.2, filed Aug. 3, 2000, pursuant to 35U.S.C. 119(a)-(d), the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0003] The present invention relates to a busbar system for a matrixconverter having a number of switching elements, in particularsemiconductor switches, which are arranged in a 3×3 matrix.

[0004] As is known, a matrix converter includes a self-commutated directconverter which allows a rigid three-phase network to be converted to asystem with a variable voltage and frequency. Known matrix convertershave a number of electrical switching elements, in particularsemiconductor switches (for example Insulated Gate Bipolar Transistors(IGBT)), which are arranged in a switch matrix. The power-electronicswitches are arranged in a 3×3 matrix, so that each of the three outputphases can be electrically connected to one input phase. On the networkside, the matrix converter or the input-side connections is or areconnected to capacitor elements, which ensure stable voltage conditionsfor the switching elements. Since there are three input phases and inputvoltages, three corresponding capacitor elements are also provided. Theconnection is made by means of the low-voltage busbar system. Only thepresence of the capacitor elements and of the low-inductance busbarsystem makes it possible for the semiconductor switches in the matrixconverter to commutate without excessive overvoltages, so that it ispossible to operate an ohmic inductive load, for example a motor. In thematrix converter, three potentials of the input voltage must beconnected with low inductance from the input capacitor elements to thesemiconductor module which forms the 3×3 switch matrix (or to themodules in a configuration in which the matrix is in the form of threephases which each have modules with three switches).

[0005] Conventional busbar systems typically include a plurality ofbusbar sections, which are arranged in three levels and are isolatedfrom one another, for which purpose appropriate insulation layers areprovided between the individual busbar system levels. Overall, thisresults in a three-layer busbar system. The low inductance is achievedby locating the busbar system levels as close to one another aspossible, with the busbar sections having a correspondingly large area.

[0006] The conventional busbar system formed with three layers, however,tends to have a high inductance, with the distance between the two outerbusbar sections determining the maximum stray inductance. Furthermore,the inner conductor is difficult to cool, since it is largely embeddedbetween the two other busbar sections. In addition, the manufacturingprocess is complex.

[0007] It would therefore be desirable and advantageous to provide animproved busbar system which obviates prior art shortcomings and has alower stray inductance and a simple design.

SUMMARY OF THE INVENTION

[0008] The invention relates to a low-inductance busbar system for amatrix converter having a number of switching elements, in particularsemiconductor switches, which are arranged in a 3×3 matrix, with thematrix converter being connected on the network side to a number ofcapacitor elements, via which three input voltage potentials can bepassed to the matrix converter. The busbar system has only two layerswhich are arranged isolated from one another in two levels. The twolevels with the various busbar sections can be closely spaced (only theinsulating layer is located between them), so that the stray inductancecan be reduced even further. The busbar sections forming the respectiverail pairs and performing the commutation in accordance with therespective switching state of the switch matrix are appropriately shapedand designed, and are suitably distributed within the levels.

[0009] Furthermore, there are no cooling problems since only twoconductor levels are provided, which can be easily cooled from theoutside. Such busbar system can also be manufactured more easily, sincethe busbar sections can be applied as flat, metallic conductor layers ina simple manner to an insulating layer of an appropriate size anddesign. For example, the conductor layers can be in the form of coatingson a board, for example, a printed circuit board (PCB). Safe andreliable processes for coating conductors on PCB are known in the artand can be used to produce the low-inductance busbar system according tothe invention.

[0010] According to one aspect of the invention, at least one busbarsection is provided for each input potential. The busbar sections can bearranged in different ways, depending on the position of the busbarsections in the two levels, while keeping the inductance of the busbarsystem as low as possible. As discussed below, this can be achievedusing a single busbar section for each input potential, or a pluralityof busbar sections for one or the other input potential.

[0011] According to another feature of the invention, a first large-areabusbar section can be provided for the first input potential in thefirst level, and second and third busbar sections, which at leastpartially overlap with the first busbar section, can be provided for thesecond and third input potentials in the second level. Two busbarsection pairs, between which the voltage is commutated, are herebyrouted alongside one another, with the potentials which are involved inone pair being located one above the other in the two layers. Thelow-inductance commutation in the third voltage pair, which is locatedin the second level, is achieved by forming eddy currents in the linerouting of the large-area first busbar section in the first level, withthe two busbar sections between which the voltage is commutated beingarranged alongside each other. Accordingly, a third busbar section isincluded for this commutation.

[0012] For reducing the stray inductance as much as possible, the firstbusbar section can cover at least 75% of the area of the two otherbusbar sections. The overlapping area should be as large as possible.

[0013] According to another feature of the invention, an associatedbusbar section can be provided for each input potential in the firstlevel and in the second level. All three possible busbar section pairsbetween which the voltage is commutated are thereby routed alongside oneanother, with one busbar section being arranged in the first level, andthe other corresponding busbar sections being arranged underneath in thesecond level. The busbar sections can be arranged such that therespective busbar sections in the first level and in the second level,which form a commutation voltage pair, are located directly opposite oneanother and overlap with one another over as large an area as possible.

[0014] According to another feature of the invention, a busbar sectionwhich is associated with the first input potential and a busbar sectionwhich is associated with the second input potential can be provided inthe first level, and a busbar section which is associated with thesecond input potential and a busbar section which is associated with thethird input potential can be provided in the second level, with thebusbar sections being arranged and designed such that the busbarsections which form one commutation voltage pair are opposite oneanother, or at least partially cover one another. Accordingly, twobusbar sections which are each associated with a different inputpotential can be provided in each level, with one of these busbarsections having a considerably larger area than another correspondingbusbar sections. The relatively large area busbar sections which arelocated in different levels and are each associated with differentpotentials and furthermore likewise form a commutation voltage pair canthen also overlap with one another. The area over with which the busbarsections in each case overlap should essentially be of the same size.

[0015] According to yet another feature of the invention, an busbarsection can be provided for each input potential in the first level andan additional large-area busbar section which forms an opposing surfacecan be provided in the second level, wherein the large-area busbarsection need not be connected to any of the three potentials and coversthe busbar sections of the first level. This feature employs a busbarsection which is not connected to any specific potential and which isincluded in the respective commutation path. The commutation processhereby also takes place by forming eddy currents in the busbar sectionwhich forms the opposing surface and is preferably at ground potential.The respective sections are sized so that the live busbar sectionscompletely overlap with the opposite additional busbar section.Alternatively, the additional busbar section can be connected to one ofthe three potentials.

[0016] According to another aspect of the invention, the invention alsorelates to a circuit arrangement comprising a matrix converter and atleast three capacitor elements, which are connected to one another via alow-inductance busbar system of the type described above.

[0017] The matrix converter can also be designed to include a pluralityof separately configured and arranged output phase modules, which can beconnected to the capacitor elements via the busbar system. Thus, thematrix converter is not a central component, but rather includesseparate phase modules, for example three phase modules, each of whichcarries a separate output phase. The busbar system can then be designedso that the capacitor elements make contact with the appropriate phasemodules. The phase modules can have a common associated capacitor block,which includes the various capacitor elements and makes contact with theindividual modules via the busbar system. Alternatively, each phasemodule can have its own capacitor block with a plurality of capacitorelements.

BRIEF DESCRIPTION OF THE DRAWING

[0018] Other features and advantages of the present invention will bemore readily apparent upon reading the following description ofcurrently preferred exemplified embodiments of the invention withreference to the accompanying drawing, in which:

[0019]FIG. 1 shows schematically in cross-section an exemplaryarrangement of busbar sections according to the present invention,

[0020]FIG. 2 shows schematically a plan view of the busbar system ofFIG. 1,

[0021]FIG. 3 shows schematically in cross-section another exemplaryarrangement of busbar sections according to the invention,

[0022]FIG. 4 shows schematically a plan view of the busbar system ofFIG. 3,

[0023]FIG. 5 shows schematically in cross-section yet another exemplaryarrangement of busbar sections according to the invention,

[0024]FIG. 6 shows schematically a plan view of the busbar system ofFIG. 5,

[0025]FIG. 7 shows schematically in cross-section another exemplaryarrangement of busbar sections according to the invention,

[0026]FIG. 8 shows schematically a plan view of the busbar system ofFIG. 7,

[0027]FIG. 9 shows an exemplary embodiment of a circuit arrangementaccording to the present invention, and

[0028]FIG. 10 shows another exemplary embodiment of a circuitarrangement according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0029] Throughout all the Figures, same or corresponding elements aregenerally indicated by same reference numerals. These depictedembodiments are to be understood as illustrative of the invention andnot as limiting in any way.

[0030] Turning now to the drawing, and in particular to FIG. 1, there isshown a schematic cross-section of a first exemplary embodiment of abusbar system according to the present invention. The illustration showsan insulating layer 1, in the illustrated example a board, such as aPCB, with busbar sections V₁, V₂, V₃ applied, for example coated, aslarge-area metallic conductor surfaces (for example made of aluminum) tothe top face and the bottom face of the insulating layer 1. Each of thebusbar sections in this exemplary embodiment is associated with aspecific input voltage potential P₁, P₂ and P₃, which is supplied viacapacitor elements which will be described in more detail with referenceto FIG. 2. In the illustrated example, the upper busbar section V₁ isassociated with the potential P₁, and the two lower busbar sections V₂and V₃ are associated with the potentials P₂ and P₃. There is nospecific required association between the input potentials and therespective busbar sections, so that the potentials may also beinterchanged in any desired manner. This applies to all the exemplaryembodiments which are described in the following text.

[0031] As can be seen, the exemplary upper busbar section V₁ is designedto be considerably broader than the lower busbar sections V₂, V₃. Theseare of such sizes and are positioned in such a way that a substantialarea is covered by the upper busbar section V₁. They should be coveredto as great an extent as possible, with an area coverage of, forexample, at least 75%. This can also be seen in the form of a plan viewin the layout illustration shown in FIG. 2.

[0032] The areas shown by dashed lines, which each represent busbarsections, are arranged in the upper level, while the surfaces shown bysolid lines, which likewise represent busbar sections, are arranged inthe lower level. As can be seen, the busbar section V₁ covers a largearea of the two busbar sections V₂, V₃.

[0033] Overall, three commutation voltage pairs, or busbar sectionpairs, are formed between which the current and voltage are commutated.The first commutation voltage pair includes the busbar sections V₁ andV₂, and the second pair includes the sections V₁ and V₃. As can be seen,these commutation voltage pairs are arranged alongside one another, withthe respective sections which participate in the commutation processbeing located opposite one another, and being isolated via theinsulation layer. The third commutation voltage pairs V₂ and V₃ arelocated alongside one another. The commutation in this voltage pair isachieved by eddy currents, which are produced in the busbar section V₁.

[0034]FIG. 2 furthermore shows the busbar system of the capacitorelements and of the respective connections to the matrix converter.Overall, three capacitor elements K₁, K₂ and K₃ are provided. In theillustrated exemplary embodiment, the capacitor elements are placed fromabove onto the configuration shown in FIG. 2. The capacitor element K₁is connected to the busbar section V₁ and to the busbar section V₂, witha suitable aperture 2 being provided in the busbar section V₁ forcontacting the busbar section V₂. Likewise, the capacitor element K₂makes contact with the busbar section V₁ and with the busbar section V₃.Both capacitor elements K₁ and K₂ are connected by the second contact toa common contact point on the busbar section V₁. Finally, the capacitorelement K₃ is connected to the two busbar sections V₂, V₃, with thecontact-forming connections in this case being passed throughcorresponding apertures 2 in the busbar section V₁.

[0035] Furthermore, each busbar section V₁, V₂, V₃ is connected to acorresponding one of connections L₁, L₂, L₃. The connections L₁, L₂, L₃are part of the matrix converter 3, which is illustrated here only inthe form of an example.

[0036]FIG. 3 shows another exemplary embodiment. The busbar sections arehere also in the form of large-area metallic conductor surface coatingsin two levels on the insulation layer 1. Overall, six busbar sectionsare used, with a respective one of the busbar sections V₁, V₂ and V₃being provided in each level. A specific input potential P₁, P₂, P₃ isassociated with each of the busbar sections V₁, V₂, V₃. The sectionalview in FIG. 3 shows that, in this embodiment, three commutation voltagepairs located alongside one another are formed, namely the pair V₁-V₂,the pair V₂-V₃ and the pair V₃-V₁, each isolated via the insulationlayer 1. The respective busbar sections which are located in one levelare slightly spaced apart from one another for isolation purposes, withthe exemplary isolation in the horizontal plane being provided via theair gap.

[0037]FIG. 4 shows a plan view of the busbar system of FIG. 3. Thebusbar sections which are located in the upper layer are shown by dashedlines, and the busbar sections which are located in the lower level areshown by solid lines. As in the previous embodiment, the respectivecapacitor elements K₁, K₂, K₃ make contact with the respective busbarsections, with appropriate apertures being provided in the respectiveconnecting section, in order to make a through-contact. Since arespective busbar section which is associated with a specific potentialP₁, P₂, P₃ is routed in each level, both busbar sections are connectedto a common connection L₁, L₂, L₃, which an appropriate configuration ofthe busbar sections. The busbar sections V₁, V₂, V₃ which run in thelower level are in each case routed in straight lines to the respectiveconductor connection L₁, L₂ or L₃, the ends of the upper busbar sectionsV₁, V₂ and V₃ are designed to be appropriately angled, and are routed tothe respective conductor connection L₁, L₂ and L₃. In the illustratedexample, the two busbar sections V₁ make contact with the conductorconnector L₁, the busbar sections V₂ make contact with the conductorsection L₂, and the busbar sections V₃ make contact with the conductorconnection L₃.

[0038] The modification illustrated in FIG. 3 shows a total of sevenisolation points, namely the isolation between the upper and lowerbusbar sections (three isolation points) as well as the respectiveisolation gaps between the busbar sections located in one level (a totalof four isolation points).

[0039]FIG. 5 shows a busbar system with a less complex isolation. Twobusbar sections are provided in each level, the busbar sections V₁ andV₂ in the upper level, and the busbar sections V₂ and V₃ in the lowerlevel. The busbar section V₁ in the upper level and the busbar sectionV₃ in the lower level are each designed to be very broad, thus ensuringthat their central sections overlap. In this embodiment as well, a totalof three commutation voltage pairs are formed, arranged alongside oneanother. The number of isolation points can in this case be reduced to atotal of five, since only two busbar sections are provided in eachlevel.

[0040] The corresponding layout of this busbar system is shown in FIG.6. The one busbar section V₁ and the one busbar section V₃ arerespectively connected to the line connection L₁ and L₃, and the twobusbar sections V₁ are connected on the top face and bottom face to thecommon line connection L₂. The capacitor elements K₁, K₂, K₃ are in thiscase also connected correspondingly, in a known manner.

[0041]FIG. 7 shows yet another exemplary embodiment. Three busbarsections V₁, V₂, V₃ are arranged in the lower level, and a single verylarge-area busbar section V₄ is provided in the upper level. While thebusbar sections V₁, V₂, V₃ are connected to a respectively associatedpotential P₁, P₂ and P₃, the busbar section P₄ is not connected to anyspecific potential, but is preferably connected to ground. Therespective commutation voltage pairs in this embodiment are formed withthe enclosure of the upper busbar section V₄, which forms a metallicopposing surface and substantially covers the busbar sections locatedunderneath. Eddy currents are produced in the busbar section V₄ duringcommutation, thus making the commutation process possible. Although thebusbar section V₄ need not be connected to a specific potential, theycan advantageously be connected to ground to provide suppression at thesame time.

[0042] The corresponding layout is shown in FIG. 8. As can be seen, eachbusbar section V₁, V₂, V₃ is connected to a respective line connectionL₁, L₂ and L₃, and the busbar sections are interconnected to thecorresponding capacitors K₁, K₂, K₃. The capacitor elements are allfitted to the modification from above, for which reason acorrespondingly large number of apertures 2 are provided in the busbarsection V₄ in order to make through-contact.

[0043] Overall, all the modifications allow a busbar system constructionin two levels, thereby obviating the disadvantages of a three-layerstructure. Furthermore, this two-layer configuration makes it possibleto produce the busbar system in a highly cost-effective manner bycoating the busbar sections onto a board.

[0044]FIG. 9 shows schematically an exemplary circuit arrangementaccording to the invention with separately provided output phases of thematrix converter. The illustrations show three phase modules 4, 5, 6,each of which with a specific associated phase. The phase modules 4, 5,6 have a common capacitor block 7 with three individual capacitorelements, with the capacitor elements being connected via theillustrated busbar system 8 to the corresponding phase modules 4, 5, 6which together form the matrix converter.

[0045]FIG. 10 shows an alternative exemplary embodiment of a circuitarrangement with separate phase modules. In this case as well, threeseparate phase modules 4, 5, 6 again each have an associated capacitorblock 7 with a number of capacitor elements. Like in the embodimentshown in FIG. 9, the individual capacitor elements are connected in alow-inductance manner via the illustrated busbar system.

[0046] While the invention has been illustrated and described inconnection with currently preferred embodiments shown and described indetail, it is not intended to be limited to the details shown sincevarious modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention. Theembodiments were chosen and described in order to best explain theprinciples of the invention and practical application to thereby enablea person skilled in the art to best utilize the invention and variousembodiments with various modifications as are suited to the particularuse contemplated.

[0047] What is claimed as new and desired to be protected by LettersPatent is set forth in the appended claims and their equivalents:

What is claimed is:
 1. In a matrix converter including a plurality ofswitching elements arranged in a 3×3 matrix, and a plurality ofcapacitor elements connected on a network side of the matrix converterand supplying corresponding three input voltage potentials to the matrixconverter, a low-inductance busbar system comprises a plurality ofbusbar sections which are isolated from one another and arranged infirst and second levels.
 2. The busbar system of claim 1, wherein thereis associated at least one of the busbar sections with each of the inputvoltage potentials.
 3. The busbar system of claim 1, wherein a firstlarge-area busbar section is associated with a first one of the inputvoltage potentials in the first level, and second and third busbarsections are associated with a second input voltage potential and athird input voltage potential in the second level, wherein the secondand third busbar sections at least partially overlap the first busbarsection.
 4. The busbar system of claim 3, wherein the first busbarsection overlaps at least 75% of an area of the second and third busbarsections.
 5. The busbar system of claim 1, wherein there is provided acorresponding one of the busbar sections for each of the input voltagepotentials in each of the first and second levels.
 6. The busbar systemof claim 5, wherein the plurality of busbar sections are so disposed inthe first and second levels that confronting busbar sections in thefirst and second levels define a commutation voltage pair.
 7. The busbarsystem of claim 1, wherein a busbar section associated with a firstinput voltage potential and a busbar section associated with a secondinput voltage potential are provided in the first level, and a busbarsection associated with the second voltage input potential and a busbarsection associated with a third voltage input potential are provided inthe second level, with the busbar sections arranged in such a way thatconfronting busbar sections define a commutation voltage pair and atleast partially overlap one another.
 8. The busbar system of claim 7,wherein overlapping areas of the confronting busbar are substantially ofsame size.
 9. The busbar system of claim 1, wherein a first number ofthe busbar sections and the input voltage potentials are disposed in thefirst level in one-to-one correspondence, and one busbar section has alarge-area and is provided in the second level for providing a countersurface, with the large-area busbar section overlapping the busbarsections in the first level.
 10. The busbar system of claim 9, whereinthe large-area busbar section is not connected to any of the three inputvoltage potentials.
 11. The busbar system of claim 9, wherein thelarge-area busbar section is connected to one of the three input voltagepotentials.
 12. The busbar system of claim 9, wherein the large-areabusbar section is connected to ground.
 13. The busbar system of claim 1,wherein the plurality of busbar sections are in the form of flatmetallic conductor layers disposed on an insulating layer.
 14. Thebusbar system of claim 1, wherein the insulating layer is formed as aboard and the metallic conductor layers are coated on the board.
 15. Thebusbar system of claim 1, wherein the switching elements aresemiconductor switches.
 16. A circuit arrangement comprising a matrixconverter including a plurality of switching elements arranged in a 3×3matrix, at least three capacitor elements connected on a network side ofthe matrix converter and supplying corresponding input voltagepotentials to the matrix converter; and a low-inductance busbar systemincluding a plurality of busbar sections which are isolated from oneanother and arranged in two levels for connecting the capacitor elementsto one another.
 17. The circuit arrangement of claim 16, wherein thematrix converter includes a plurality of phase modules which areconnected to the capacitor elements via the busbar sections.
 18. Thecircuit arrangement of claim 17, and further comprising a capacitorblock which commonly houses the capacitor elements and is connected tothe plurality of the phase modules.
 19. The circuit arrangement of claim18, and further comprising a plurality of capacitor blocks, wherein eachof the capacitor blocks includes a plurality of said capacitor elementswherein the capacitor elements are arranged in a plurality of capacitorblocks, wherein the capacitor blocks and the phase modules are placedinto one-to-one correspondence.